This invention relates to fence building and more particularly to a mobile machine and unit for forcing fence posts into the surface of the earth.
1. Field of the Invention
It is known to utilize a drop hammer mounted on the bed or frame of a truck for forcing posts into the surface of the earth. However, a drop hammer has several drawbacks. For example, on account of the mass of a drop hammer the frame supporting it for vertical reciprocating movement must be rigidly attached to the bed or frame of a truck. Further, accurate soil penetrating depth is not easily controlled and a drop hammer usually damages the top end of the relatively thin gauge wall of tubular chain link fence posts.
This presents additional problems, for instance, it is not likely that the drop hammer will drive vertically when the wheels of the truck are located on uneven ground in the field or location adjacent the site where the post must be driven. Attempting to orient the drop hammer supporting frame vertically requires considerable time and effort on the part of more than one workman which delays the work progress and increases the cost thereof.
Further, in wire fences for confining substantially any animal within or out of a selected area, the fence wire height varies in accordance with the animals to be confined. For example, 12 to 15 or more feet (3.66 to 4.57M) as opposed to 5 to 8 feet (1.52 to 2.44M). The posts supporting a wire fence must have a similar height.
This invention overcomes the above outlined problems by providing a post driving unit mounted upon a mobile vehicle in which the post driver supporting beam is horizontally rotatable and vertically pivotable for accommodating substantially any post length in the above described range desired to be driven into the surface of the earth. The axis of the driving unit is vertically oriented by gravity.
2. Description of the Prior Art
U.S. Pat. No. 2,844,006, issued Jul. 22, 1958 to Lutz et al for POST DRIVER ATTACHMENT discloses a pair of tractor mounted booms hydraulically pivoted vertically at their ends opposite the tractor for supporting a drop hammer frame pivotally connected with the ends of the booms remote from the tractor.
The drop hammer frame is supported from the booms by horizontal right angular disposed mounting axes permitting the depending end portion of the drop hammer frame to be plumbed by gravity when positioned over the upper end of a post being driven into the ground. The drop hammer is lifted by tractor power and released for impacting on the top of the post to perform the desired action.
U.S. Pat. No. 3,117,635 issued Jan. 14, 1964 to Terry Industries for SELF-PROPELLED POST DRIVER discloses a post driving apparatus mounted on a tractor supplying hydraulic and air power for operating a jack hammer depending from a boom mounted on a mast for movement in two generally horizontal orthorgonal axes. The mast is pivotally mounted on the tractor and a pair of cylinders are manipulated to orient the mast vertically and afford versatility and placement of the post.
Other state-of-the-art patents generally relate to road working machines or to a combination auger and post driver such as disclosed by U.S. Pat. No. 3,696,625, issued Oct. 10, 1972 to Alexander for POST IMPLANTING METHOD AND VEHICULAR APPARATUS THEREFOR.
This patent provides a truck mounted auger which bores a hole at the post site and subsequently drives a post, by a drop hammer, into the hole previously excavated.
This invention is distinctive over the above named and other patents by removably mounting a post driving apparatus on the rearward end portion of a farm tractor. The post driving apparatus includes a horizontally rotating and vertically pivoting boom and a wire line block and tackle supporting an air pressure driven impact hammer vertically oriented by gravity.